Rockwool
A mineral-fiber growing substrate formed by spinning molten rock into fibers and shaping them into propagation plugs, blocks, or slabs.
Horticultural rockwool provides a porous structure that holds both water and air around roots. It contributes little nutrient content, so irrigation solution supplies nearly all mineral nutrition in a soilless cannabis system.
Product density, fiber orientation, container geometry, root development, and irrigation history affect its water distribution and dryback Dryback The decrease in a growing substrate's water content between irrigation events, commonly tracked as a change in volumetric water content. . Water content alone does not describe how tightly the remaining water is held.
New rockwool products commonly require saturation and pH conditioning according to the manufacturer's instructions. During production, growers track water content, electrical conductivity, pH, irrigation volume, and runoff together rather than treating the substrate as chemically featureless.